This invention relates to resinous compositions, more particularly to hot melt compositions suitable in coating and adhesive applications.
There have been proposed numerous adhesive compositions and particularly, hot melt adhesive compositions of 100 percent solid type which have found extensive application in book bindings, packaging, woodcrafts and the like for their excellent fireproofness, reduced curing time and ease of handling. Hot melt adhesive compositions are solid at room temperature and melt with heat so that they may be coated in molten condition onto a desired substrate such as cloth and paper and cooled to cure thereon. Amongst the important properties required in order that the adhesive compositions exhibit good and uniform adhesiveness with respect to different substrates, there should always be considered the question of whether they have sufficient resistance to heat or thermal stability particularly at low temperature.
Conventional hot melt adhesive compositions usually comprise, as a base polymer, an ethylene copolymer such as ethylene-vinyl acetate copolymer (EVA) and ethylene-acrylate copolymer, or a thermoplastic material such as polyethylene, thermoplastic rubber, polyamide, polyurethane, polyester, the base polymer being blended with a tackifying resin, a viscosity regulator and waxes to improve adhesiveness and melt viscosity. Of the above listed examples of base polymer, wider use has been made of EVA and ethylene-acrylate for their low cost, excellent yieldability, and high thermal stability. The tackifying resin has been preferably a naturally occurring resin such as rosin and terpene resin, the former being highly adhesive and pliable or flexible at low temperature, and the latter being thermally stable. However, since these resins originate from limited natural resources, they are objectionably costly. Attempts have been made to explore the possibility of petroleum resins comparable in adhesiveness, thermal stability, and low temperature characteristics to rosin and terpene resin, but with no satisfactory success to date.